Bioelectrical Impedance Phase Angle Value and Prolongations of PR and Corrected QT Intervals in Patients Undergoing Dialysis

Abstract

Introduction: Phase angle value, derived from bioelectrical impedance analysis, represents the body cell mass and nutritional status of patients undergoing hemodialysis. Although the phase angle value has clinical significance in these patients, its relationship with electrocardiogram (ECG), another clinically relevant bioelectrical examination, has not yet been well clarified.

Methods: Two hundred and twenty-four patients undergoing dialysis (80 females and 144 males; mean ± SD, 72.2 ± 12.0 years old; 117 diabetic and 107 nondiabetic patients) were studied retrospectively. Multifrequency bioelectrical impedance analysis was performed immediately after the end of dialysis therapy. The phase shift was geometrically converted into a phase angle value. The ECG was recorded simultaneously, and the upper limits of the PR interval, QRS width, and corrected QT interval (QTc) were set at 0.20, 0.12, and 0.44 s, respectively. The geriatric nutritional risk index (GNRI), a representative nutritional index, was also determined. In addition, we examined the incidence of cardiac events, including heart failure, myocardial infarction, cardiac revascularization procedure, cardiac arrhythmia, and cardiac death, or all-cause death.

Results: Of 224 patients undergoing dialysis, the prolongation of the PR interval, QRS width, and QTc was found in 30.7, 17.4, and 62.1%, respectively. The prevalence of QTc prolongation was higher in females and diabetic patients than in males and nondiabetic patients. An inverse relationship between phase angle value and QTc was observed only in males and nondiabetic patients. The relationships of GNRI both with phase angle value and QTc were stronger in males and nondiabetic patients. In addition, PR interval was inversely correlated with a phase angle value only in nondiabetic patients. No significant correlation was found between phase angle value and QRS width. Five-year survival probability for the composite endpoints was significantly worse in patients with lower phase angle values. QTc prolongation was associated with survival in males and nondiabetic patients. Prolonged PR was associated with survival in nondiabetic patients.

Discussion: Relationships between phase angle value and ECG findings were demonstrated in patients undergoing dialysis, especially in males and nondiabetic patients. Although the phase angle value has been considered as an index for evaluating nutritional status, another clinical application of phase angle value in predicting cardiac complications seems to be useful.

Keywords: Bioelectrical impedance analysis; Corrected QT interval; Hemodialysis; PR interval; Phase angle value.